Luminescent ZrO2:Pr3+ , SiO2:Pr3+, ZnO:Pr3+ and ZnS:Pr3+ nanophosphors were synthesized by a sol-gel method, dried, ground and annealed in air at 600oC (SiO2:Pr3+, ZrO2:Pr3+, ZnO:Pr3+ and ZnS:Pr3+) or 280oC (ZrO2:Pr3+). ...